External rupa is material, of course. For example, a gold ring is made of atoms and molecules.
- When person X sees that ring, a mental image of it is grasped by the mind. That is the ‘internal rupa.’
There are five mental enoties associated with that ‘internal rupa‘:
- Rupa or Rupakkhandha: It registers the size, colors, shape, etc. associated with the gold ring. Furthermore, the mind compares seeing such objects in the past and matches those past experiences to recognize the object as a gold ring. That is why it is called ‘rupakkhandha‘ or an ‘aggregate or collection of rupa.’ That is a very simple explanation of a deeper subject, but a starting point.
- Vedana or Vedanakkhadha: The mind may ‘feel’ a sensation of pleasure seeing the gold ring. Suppose you saw it at the dentist’s office while waiting for your appointment. Someone may have accidentally dropped it.
- Saññā or Saññākkhandha: Recognition of the object as a gold ring. It also incorporates any value that is placed on it. The gold ring could be expensive.
- Saṅkhāra or Saṅkhārakkhndha: Thoughts that arise related to the gold ring. You may consider keeping it for yourself, instead of handing it over to the receptionist, in case the owner comes looking for it. If so, then greed would have arisen in you.
- Viññāṇa or Viññāṇakkhandha: Overall mental impression of the ring and any future plans regarding it. If you decide to keep it, you may think about giving it to your wife or girlfriend as a gift. Or you may decide to sell it.
That is a very basic explanation. The mind is extremely fast. All those things happen within a split second.
- Detailed explanations in “The Five Aggregates (Pañcakkhandha).”
